First of all:
1. Injection speed of plastic molding machine:
The injection speed of the molding machine is relatively slow, the plastic material will have more heat loss in the mold cavity, the flow viscosity will increase, and the pressure loss will also increase; higher injection speeds can often get higher accuracy, compared with no deformation The molded products are only molded through areas such as small meat thickness, drastic changes, corners, etc., and are prone to poor appearance. At the same time, problems such as poor exhaust, burrs, and incorrect switching of holding pressure are prone to occur.
2. Switching parameters for holding pressure:
If you switch too early, the size of the finished product is likely to be insufficient, and even short shots and surface depressions will occur. On the contrary, excessive compression will be formed. If the size is small, the size will be too large, flashing, whitening, deformation, etc., and the mold will be damaged if it is large;
The switching of holding pressure usually has control methods such as injection stroke (setting of position) and time.
3. Setting parameters of holding pressure size:
If the holding pressure is too high, overfilling will occur, which will cause the plastic material that has entered the cavity to flow backward;
The correct and appropriate holding pressure setting should ensure that the screw can continue to advance to the lower pressure of the target point after passing the holding pressure switching point; in the holding phase, the pressure in the mold cavity gradually decreases due to the cooling of the plastic, so the protection The pressure should be lowered appropriately, otherwise it is easy to form high pressure and cause residue.
4. Setting parameters of pressure holding time:
The holding time should be maintained until the gate is condensed. Too long does not make much sense, but if the time is too short, it is easy to reverse flow, which makes the position near the gate easy to dent and insufficient size;
Whether the holding time is appropriate or not should usually be judged by the stability of the weight;
If the gate is small, the mold temperature is low, and the pressure holding time should be set short. If the situation is opposite, set a longer time.
5. Setting parameters of cooling time:
The plastic is cooled in the mold cavity, most of which start at the end of the holding pressure switch and the mold opening. The theoretical cooling time = holding pressure time + post cooling time;
The required theoretical time should be based on the principle that the product can be ejected smoothly (without deformation), and its length varies with the thickness of the molded product, the material, and the cooling rate of the mold;
Gate thickness and mold temperature will affect the holding time (the cooling time set by the machine, that is, the post-cooling time). If the gate is large and the mold temperature is high, the holding time should be appropriately lengthened. Otherwise, the holding time should be appropriately reduced. .
6. Setting parameters of mold temperature:
If the mold temperature is set too low, the melt will flow in the mold cavity, and the temperature will drop faster, which will increase the flow resistance of the material, so the pressure loss will increase, the internal stress will increase, and the internal pressure of the mold cavity will increase.
7. High mold temperature setting:
Increase the crystallinity of the molded product and a more uniform structure, reduce the residual internal stress, deformation and increase the strength, reduce the flow resistance of the material during filling, reduce the pressure loss, and make the product appearance glossy, but it is prone to burrs, which increases the position near the gate Reduce the dent in the far gate position, make the bonding line smaller, and increase the cooling time.
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